Adam Bandt has secured re-election in Melbourne, following a sizeable swing to the Greens in the seat.

With more than half of the vote counted, Bandt has 43.7% of the primary vote, an 8% improvement on his total in 2010.

On a disastrous night for Labor, its Melbourne candidate Cath Bowtell has fared worse than expected, down 12% on 2010.

Bowtell’s primary vote of 27% in a seat that was held by Labor for 100 years is just 6% ahead of Liberal candidate Sean Armistead. She has officially conceded defeat to Bandt in a speech to party volunteers.

In a frenzied Greens election night gathering in west Melbourne, Bandt vowed to take on Tony Abbott's "brutal" agenda.

He told Guardian Australia: “A large proportion of people doesn’t want a race to the bottom from the two old parties in order to beat up on refugees.

“People in Melbourne saw the Greens as a strong and realistic alternative and we got support across the political spectrum, from Liberals who want small ‘l’ liberalism and Labor voters who want compassion.

“I sensed there was a general disillusionment among voters around the standard of debate. There’s been no vision from the main parties.”

Bandt said it was not certain whether he would vote along similar lines to Labor in the new parliament.

“Labor needs to work out what they stand for, they have been in lockstep with Tony Abbott on far too many issues,” he said. “Greens are the only alternative. The people of Melbourne are the only ones who will stand up to Tony Abbott’s brutal agenda.

“We will wait on the Senate results, but I’m hopeful we’ll retain the balance of power there. We’ll also wait on Tony Abbott’s real agenda, which will soon unfurl itself, I’m sure.

“In terms of voting with Labor, it depends where Labor votes. Will they hold the line over carbon pricing legislation? That’s a big question.”

Bandt had to raise his primary vote by 4% to keep the seat, due to Liberal preferences flowing to Labor ahead of the Greens.